Add opcode for notification in configdb.py

[batmancn]

Hi all,

I think it's good to add opcode for notification in configdb.py to verify the difference between these:

"AAA": null
"AAA": {}

So I want to contribute a PR with this patch as bellow, but I have no access for push and merge PR? How to deal with this?

commit f547f9c02347e7b42962278005bcba973892a18b
Author: sam <batmanustc@gmail.com>
Date:   Tue Nov 27 11:31:27 2018 +0800

    add opcode in redis notification

diff --git a/src/swsssdk/configdb.py b/src/swsssdk/configdb.py
index e255979..87cad6e 100644
--- a/src/swsssdk/configdb.py
+++ b/src/swsssdk/configdb.py
@@ -76,10 +76,10 @@ class ConfigDBConnector(SonicV2Connector):
         if self.handlers.has_key(table):
             self.handlers.pop(table)

-    def __fire(self, table, key, data):
+    def __fire(self, table, key, data, op_str='add'):
         if self.handlers.has_key(table):
             handler = self.handlers[table]
-            handler(table, key, data)
+            handler(table, key, data, op_str)

     def listen(self):
         """Start listen Redis keyspace events and will trigger corresponding handlers when content of a table changes.
@@ -94,7 +94,11 @@ class ConfigDBConnector(SonicV2Connector):
                     if self.handlers.has_key(table):
                         client = self.redis_clients[self.CONFIG_DB]
                         data = self.__raw_to_typed(client.hgetall(key))
-                        self.__fire(table, row, data)
+                        op = client.keys(key)
+                        op_str = 'add'
+                        if len(op) == 0:
+                            op_str = 'del'
+                        self.__fire(table, row, data, op_str)
                 except ValueError:
                     pass    #Ignore non table-formated redis entries